Health

The benefits and hazards of liquid oxygen

Liquid oxygen therapy is the medical process of providing additional oxygen to patients

 
By Manas Ranjan Senapati
Published: Tuesday 13 July 2021

Liquid oxygen has a pale blue colour and is a cryogenic liquid. Cryogenic liquids are liquefied gases that have a normal boiling point below -238 degrees Fahrenheit (-150 degrees Celsius).

Oxygen is often stored as a liquid, although it is used primarily as a gas. The low temperature of liquid oxygen and the vapour it releases poses a serious burn hazard to human tissue. Materials which usually burn in ambient air will burn more vigorously in oxygen.

In commerce, liquid oxygen is classified as an industrial gas and is widely used for industrial and medical purposes. Liquid oxygen is used as an oxidant for liquid fuels in the propellant systems of missiles and rockets. 

Oxygen is widely applied in the metal industries in conjunction with acetylene and other fuel gases for metal cutting, welding, hardening, cleaning and melting.

Liquid oxygen therapy is the medical process of providing additional oxygen to a patient who cannot get enough oxygen on their own. Conditions such as asthma, cystic fibrosis, dysphasia, chronic obstructive pulmonary disease, heart failure, lung disease and pneumonia can be treated by liquid oxygen therapy.

Contact with liquid oxygen can cause severe skin and eye irritation and burns as well as frostbite. Normally, air contains 21 per cent oxygen and oxygen is essentially nontoxic.

No health effects have been observed in people exposed to concentrations up to 50 per cent liquid oxygen at one atmosphere pressure for 24 hours or longer. Inhalation of 80 per cent oxygen at one atmosphere for more than 12 hours can cause irritation of the respiratory tract, nausea, dizziness, muscle twitching, vision loss, coughing, nasal stuffiness, sore throat and chest pain.

A characteristic neurological syndrome can be observed when pure oxygen is inhaled at pressures greater than two or three atmospheres. Signs and symptoms include nausea, dizziness, vomiting, tiredness, light-headedness, mood changes, euphoria, confusion, incoordination, muscular twitching, burning / tingling sensations (particularly of the fingers and toes) and loss of consciousness.

Characteristic epilepsy-like convulsions, which may be preceded by visual disturbances such as loss of peripheral vision, also occur. Continued exposure can cause severe convulsions, leading to death. The effects are reversible after reduction of oxygen pressure.

The following are the hazards liquid oxygen is associated with:

  • Exposure to cold temperatures that can cause severe burns
  • Over pressurisation due to the expansion of small amounts of liquid into large volumes of gas in inadequately vented equipment
  • Oxygen enrichment of the surrounding atmosphere
  • The possibility of a combustion reaction if the oxygen is permitted to contact a noncompatible material.

Some common materials like asphalt, kerosene, cloth, wood, paint, tar and dirt containing oil or grease can react violently with liquid oxygen at certain pressures and temperatures.

Personnel must be thoroughly familiar with properties and safety considerations before being allowed to handle liquid oxygen and its associated equipment.

Views expressed are the author’s own and don’t necessarily reflect those of Down To Earth 

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